Summary from Shoujo Manga Maniac :
Tsubaki is a girl who loves making her younger sister's hair pretty every morning, but she doesn't think that kind of style suits herself! The day of her High School Beginning Ceremony, after she failed in being the top student (who usually makes the ceremony speech), she finds herself sitting next to the actual top student of the first years, the worst rude guy ever, Kyouta. She ends up cutting his hair on purpose because of the bad things he says to her. Kyouta demands that Tsubaki pay him back with her body, but Tsubaki fixes his hair instead - making it even shorter! After that, Kyouta unexpectedly kisses Tsubaki and swears that he'll take all her firsts.